Apparatus for producing composite filaments



May 2, 1967 c. J. HOLLANDSWORTH, JR 3,316,589

APPARATUS FOR PRODUCING COMPOSITE FILAMENTS Original Filed Dec. 3l, 1962 2 Sheets-Sheet 2 United States Patent Ofice 3,316,589 APPARATUS FR PRODUClNG COMPOSITE FILAMENTS Charles Jarman Hollandsworth, Jr., Martinsville, Va., assgnor to E. I. du Pont de Nemours and' Company, Wilmington, Del., a corporation of Delaware Original application Dec. 31, 1962, Ser. No. 248,640, now Patent No. 3,244,785, dated Apr. 5, 1966. Divided and this application Uct. 27, 1965, Ser. No. 505,338

3 Claims. (Cl. 18-8) This is a division of my copending application Ser. No. 248,640, led Dec. 31, 1962, now Patent No. 3,244,785. The invention relates to an apparatus which is useful in the production of sheath-core composite filaments from synethetic polymers.

In the production of sheath-core filaments of the type disclosed by Breen in U.S. Patent No. 2,987,797, certain difficulties are encountered with known spinning equipment. These difiiculties are primarily associated with inaccurate and inconsistent control of the relative positions of the sheath and core. Manifestly, good control in these respects is necessary to the production of uniform filaments.

The most important object of this invention is to provide an improved apparatus for the production of sheathcore filaments. More particularly, the objective is to provide for the accurate and consistent location of a core in the filamentary sheath.

These and other objectives have been achieved with a spinneret pack which includes sandwiched filter block and spinneret plate elements, one of which is recessed to present a `distribution space. The filter |block element has separate cavities for distinct molten polymers `and at least one distribution passage connecting each cavity with the distribution space. The spinneret plate element has at least one spinning orifice communicating with the distribution space through branched flow passages, one of which is coaxial with a distribution passa-ge in the filter block element.

Other objectives and advantages will be apparent from the `following descriptions and example wherein reference is made to the accompanying drawing in which:

FIGURE 1 is a schematic illustration of equipment useful in carrying out the exemplified process;

FIG. 2 is a partial transverse sectional view through an operable embodiment of the spinneret pack shown schematically in FIG. l;

FIGS. 3 and 4 are sectional views taken on lines III- III and IV-IV of FIG. 2, showing also the viscous flow in the respective passages; and

FIG. 5 is a similar but enlarged sectional View taken on line V-V of FIG. 2.

The various .procedures described in the example have been shown schematically in FIG. l, including the for-mation of filaments in a spinneret and their passage through a quenching chamber 12 to a package 14. Subsequently, the filament bundle is withdrawn from the package and advanced over a feed roll 16, in several wraps around a draw pin 18, to a draw roll 20, whence it passes under low tension through a crimping chamber 22 in which the filaments are crimped into helical form by exposure to a 'heated gaseous fluid. From chamber 22, the crimped bundle is guided to snubbing pins 24, 26 and delivered to a package 27 by rolls 28, 29.

Referring to FIG. 2, the spinneret pack chosen ttor purposes of illustration includes `a filter block 30 having separate filtration cavities 32, 34 from which different viscous polymeric materials are discharged through distribution passages 36, 38. The material from cavity 32 passes through a distribution space 40 between block 30 and a spinneret plate 42 and enters flow passages 44, 46, as indicated by arrows. The core material is discharged 3,316,589 Patented May 2, 1967 axially yfrom distribution passage 38 into flow passage 46, i.e., passages 38, 46 are coaxial land. the different polymeric materials flow through passage 46 in substantially concentric paths (FIG. 3). As illustrated, the sand-wiched surface of filter block 30 is recessed except at the location of passage 38 where there is a concentri-c, cylindrical boss 35 projecting into space 40. Boss 35 has a flat bottom. Its width relative to the diameter of passage 46 and its spacing from plate 42 are important design considerations, the proper choice of which insures the concentric sheath-core distribution in passage 46. At the juncture of passages 44, 46, the materials are com- -bined in an essentially side-by-side relationship and extruded through a reduced spinning passage having an orifice 48. Additional lorifices are aligned longitudinally of spinneret 10 and are supplied Iby distribution passages corresponding to those shown at 36, 38 from the two cavities 32, 34.

The different polymeric starting materials are, of course, selected in such a manner that the sheath and core -components of the final filament exhibit different shrinkage characteristics `when exposed to heat `and/or swelling media whereby the desired crimped configuration is attained.

Example An evaporator is charged with 370 gallons of an aqueous solution of hexa-methylenediammonium sebacate (6-10 salt solution) containing 1,132 pounds of dry salt and 260 gal. of an aqueous solution of hexamethylenedia-mmonium adipate (6-6 salt solution) containing 1,163 lbs. of dry salt .and the resulting solution is heated at 13 p.s.i.g. until the temperature reaches 132 C., giving a salt concentration of approximately The solution is then transferred to an autoclave, heated to a tempcrature of about 205 C. and brought to -a pressure of 250 p.s.i.g. At this point, sufficient 20% aqueous titanium dioxide slurry is added to give a concentration of 0.3% Ti02 in the final polymer. The solution is then heated at 250 p.s.i.g. until the temperature reaches 225 C. The pressure is then reduced over a period of minutes to atmospheric and the temperature is in-creased to 250 C. The polymer is then held, `at atmospheric pressure, for 30 minutes at a temperature of Z50-260 C., extruded `under p.s.i.g. nitrogen in the form of a ribbon, quenched on a water-cooled casting Iwheel and cut into 5/s-inch flake in the conventional manner. The copolymer, consisting of 50% polyhexamethylene adipamide and 50% polyhexamethylene sebacamide, has a relative viscosity of 45.

Polyhexamethylene adipamide (6 6 nylon) flake having a relative viscosity of 46.5 is also prepared in the conventional manner. The two flakes (6-6 and 6-6/6-10) are fed separately t-o a dual screw melter where the flake is first conditioned by exposure to humiditied nitrogen at C. and then melted and pumped to `a spinneret assembly of the type shown in FIGS. 1 and 2. The relative viscosity of the 6-6 fiake after conditioning is 50 and that of the 6-6/6-10 copolymer flake is 55. The melt temperature of the 6-6 is 290 C. and that of the 6-6/6-10 is 282 C. The two polymers are then extruded, with the 6-6/6-10 copolymer as the core, from a spinneret which contains seven orifices arranged in a straight line. The clearance between boss 35 on block 30 and spinneret plate 42 is 0.003 inch. The filaments are set by quenching, using a 60-inch chimney and an air temperature of 45 C., and wound into a package 14 at 461 y.p.m. The yarn is subsequently withdrawn from the package and drawn to a ratio of 4.29 over an unheated draw pin 18 situated between r-olls 16, 20 to give a final yarn denier of 45. The yarn is passed from 4the second draw roll through a tubular crimping chamber 22, three inches in length, at 563 y.p.m In the chamber, the yarn is heated by -pasisng 0.5 cubic foot/minute of hot air at 30-38 p.s.i.g. through the chamber to give an air temperature of 201-208 C. at the exit. The yarn which is under low tension in the crimping chamber is crimped into helical form as indicated at 23 and then led over snubbing pins 24, 2-6 to remove the crimp by stretching the yarn slightly. The crimpable yarn is then wound into a package 27.

When transverse cross-sections of the yarn are prepared and examined microscopically, the cross section is observed to be substantially as shown in FIG. 5. When this procedure is repeated on numerous samples, it is found that placement of the core within the sheath remains substantially constant. By comparison, sheathcore yarns made by prior art processes are found to vary considerably in this respect from sample to sample, the placement of the core Within the sheath varying considerably, thus contributing to nonuniform crimping action when the yarn is crimped and therefore to uneven texture in knit fabrics.

When the yarn `of this invention is exposed to hot water or steam, it crimps in a very uniform fashion and the crimp diameter and crimp elongation are quite uniform. The crimp elongation at a load of 0.0012 g.p.d, determined as described in U.S. 2,987,797 (except that the yarn is crimped by exposure to steam at atmospheric pressure), is 13%. Then the yarn is knit into a welt fabric for use in womens semi-stretch hose with leg yarn from two-component side-by-side 15 denier monoiils wherein one component is 6-6 nylon and the other 6-6/6-10 copolymer. The fabric has a very uniform texture and performs well.

The spinneret pack of this invention facilitates accurate control of the thickness of the sheath in an eccentric sheath-core filament, thus insuring a uniformly crimped fiber and consequently the necessary uniformity in fabrics. While some success has been achieved with packs through which the sheath and core materials flow asymmetrically into a capillary, the results have not been satisfactory for commercial production.

In carrying out the process disclosed herein, it is nec` essary that close tolerances be maintained on the various parts of the apparatus in order that filament-to-iilament uniformity be achieved. In particular, passages 38, 46 must be concentrically aligned and the space between projection 35 and plate 42 as well as the dimensions of passages 36, 38, 44, 46 must be interrelated. Furthermore, there interrelationships must be correlated with the viscosities of the two polymers employed in order to insure a proper and uniform sheath-core distribution.

While the process of this invention is preferably used in the production of sheath-core filaments having kidneyshaped cores of the type disclosed by Breen and shown herein in FIG. 5, it may also be used to advantage for producing other types of sheath-core filaments as well as in the production of sheath-core filaments containing components selected from various groups of synthetic fiber-forming polymeric materials, as disclosed in my copending application. These and other variations and modifications of the illustrated pack and the exemplified procedures may be accomplished without departing from the spirit Iof the present invention which is accordingly intended to be limted only by the scope of the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A spinneret pack comprising sandwiched filter block and spinneret plate elements, one of said elements being recessed to present a distribution space therebetween, said filter block element having separate cavities for distinct molten polymers and at least one distribution passage connecting each cavity with said space, said spinneret plate element having at least one spinning orifice in communication with said space through branched flow pasages, one of said distribution passages being coaxial with and having a lesser diameter than one of said fiow passages.

2. The spinneret pack of claim 1 wherein the sandwiched surface of said filter block element is recessed and wherein said filter block element has a cylindrical boss projecting into said space at the location of said coaxial distribution passage, said boss having a flat bottom and thereby presenting a plateau adjacent said spinneret plate element.

3. The spinneret pack of claim 2 wherein said boss is concentric with said coaxial passages and of substantially greater diameter than said coaxial fiow passage.

References Cited by the Examiner WILLIAM J. STEFHENSON, Primary Examiner. 

1. A SPINNERET PACK COMPRISING SANDWICHED FILTER BLOCK AND SPINNERET PLATE ELEMENTS, ONE OF SAID ELEMENTS BEING RECESSED TO PRESENT A DISTRIBUTION SPACE THEREBETWEEN, SAID FILTER BLOCK ELEMENT HAVING SEPARATE CAVITIES FOR DISTINCT MOLTEN POLYMERS AND AT LEAST ONE DISTRIBUTION PASSAGE CONNECTING EACH CAVITY WITH SAID SPACE, SAID SPINNERET PLATE ELEMENT HAVING AT LEAST ONE SPINNING ORIFICE IN COMMUNICATION WITH SAID SPACE THROUGH BRANCHED FLOW PASAGES, ONE OF SAID DISTRIBUTION PASSAGES BEING COAXIAL WITH AND HAVING A LESSER DIAMETER THAN ONE OF SAID FLOW PASSAGES. 